Contacting columns generally consist of a cylindrical enclosure provided with internal contacting elements promoting exchange between the fluids. In the column, the fluids can circulate in a cocurrent or a countercurrent flow. In general, the column allows to provide intimate contact between an ascending gas phase and a descending liquid phase. The contacting elements that increase the contact surface between the fluids can be trays, structured packings, i.e. the juxtaposition of several unitary elements arranged in an ordered manner, corrugated sheets for example, or random packings, i.e. anarchic piles of unitary elements, for example rings, spirals.
Structured packings can consist of folded sheets arranged in an organized manner as big blocks, as described for example in documents U.S. Pat. No. 3,679,537 and U.S. Pat. No. 4,296,050. The new generation of random packings generally consists of metal elements provided with perforations and arc portions with sophisticated shapes.
Structured packings afford the advantage of providing a large geometric area for a given representative diameter, generally the hydraulic diameter of the channels, however the effective area is less than or close to the geometric area thereof. A contrario, random packings provide rather low geometric area values in relation to the characteristic size thereof, but they can have effective transfer areas greater than the geometric areas thereof.
Patent application US-2010/0,213,625 describes a packing combining the advantages of structured packings and the advantages of random packings. Such a structured packing is so designed as to exhibit the characteristics of random packings inducing in particular liquid detachment from the surface of the packing and allowing to develop an effective area substantially greater than the geometric area thereof. This packing (FIG. 1) consists of a pile of plates (FIGS. 2, 3A and 3B) comprising corrugations, each plate being inscribed between two parallel planes, the distance between said planes ranging between 5 and 50 mm. The corrugations form a succession of positive (top of a channel, CA2) and negative (hollow of a channel, CA1) edges comprising fins inscribed between said two parallel planes. The fins are formed by cutting and deforming a band B. Notches C1 and C2 are cut out in band B. Notches C1 and C2 form an angle of 90° to the principal direction of the channels. Band B remains secured to the plate at ends E1 and E2. Band B is deformed so as to follow a triangular shape substantially symmetrical to the initial shape thereof, in relation to the meridian plane P. The width L of a band B is approximately equal to the distance between two contiguous bands along a channel (between 1 and 15 mm). Direction (D) of the edges of a plate forms a non-zero angle to the direction (D′) of the edges of an adjacent plate. The positions of two consecutive plates are such that the principal directions of the edges of each one of the two plates range from 60° to 90°.
FIG. 4 and FIG. 5 respectively show two possible contacts between two consecutive plates. A contact between two plates is referred to as good when it occurs between a positive edge of a plate and a negative edge of an adjacent plate. In FIG. 4, there is a match between two opening-free zones and a good contact between the plates so that there is no interpenetration risk. In FIG. 5, there is a match between, on the one hand, an opening-free zone (lower plate) and, on the other hand, a zone provided with an opening (upper plate); there is thus no good contact between the plates so that they can interpenetrate, therefore no satisfactory setup is possible with an embodiment compatible with an industrial production.
The likelihood of bad contacts is illustrated in FIG. 6. This figure corresponds to a 2D view of two superimposed plates. It can be noted that, despite some zones with good contacts (circles in dotted line), there is a large number of bad contacts (circles in solid line). When mounting industrial packing blocks, the many plates making up a block are tightly held against one another and not having enough contact points results in failure to respect the total block thickness; there are zones with entangled plates harmful to the flow and other zones with too great a spacing, with possible gas or liquid bypass.
In order to maintain the packing performances, it is essential to provide good mounting of the plates in relation to one another, i.e. tangle-free mounting.
The object of the invention thus relates to a packing combining the advantages of structured packings and the advantages of random packings, such as the packing described in document US-2010/0,213,625, wherein the number of good contacts is maximized by a fin length difference between one channel and the neighbouring channel.